Andy Roddick developed back spasms during his opening match at the Western & Southern Open on Tuesday, setting up a two-set loss that left questions about his health heading into the U.S. Open.
Wild card Venus Williams survived a three-set opening match, another encouraging win coming off her Olympic gold medal in doubles with sister Serena.
Later Tuesday, Serena Williams beat Eleni Daniilidou of Greece 6-3, 6-4, overcoming 42 unforced errors as she struggled to get readjusted to a hard court.
Roddick, who has played through a sore shoulder this summer, developed a new concern as he lost to a player who was in the draw as an injury replacement.
He got treatment for his back during the second set of his 7-6 (4), 6-3 loss to France's Jeremy Chardy, who replaced injured No. 9 seed John Isner. Roddick had won all three of his career matches against Chardy.
Roddick said his back started bothering him a few days ago and he aggravated it Tuesday.
"I felt fine early on, and then I had one lunge forehand and ... you know, we have all had it," he said. "The back kind of goes out or spasms a little bit. It got progressively worse."
Roddick won the Atlanta Open in July despite a sore right shoulder. He lost to Novak Djokovic 6-2, 6-1 in the second round at the Olympics, a match that lasted only 54 minutes, but arrived for the tournament in suburban Cincinnati feeling good about his health and his game.
The good feeling didn't last long.
After the third game of the second set, he had a trainer come over to help him stretch his back and shoulders. He managed only one break point during the 1-hour, 33-minute match. Roddick left the court quickly with his head down.
Roddick said his shoulder felt fine. He's not sure if his back will force him to curtail his preparation for the U.S. Open, which starts Aug. 27.
"We will know more in two, three days than we do now," Roddick said. "So it's tough for me to say what side of the fence I'm sitting on. I don't know where I'm going to be in two or three days."
Williams is trying to get in position to make a deep run at the U.S. Open, from which she had to withdraw last year because of an immune system disease that causes fatigue and sore joints. She beat 12th-seeded Maria Kirilenko of Russia 6-3, 6-7 (5), 6-2 in a match that lasted 2 hours, 23 minutes, serving 11 aces.
Along with the Olympic gold medal, it's been a good few weeks for Williams, who is learning how to manage the symptoms of her disease.
"I'm doing a lot better than this time last year," she said. "So much better than a couple months ago as well. I also am learning to deal with everything a lot better. If I wake up and I don't feel great, then I would panic and lose my match 2-1. Now I realize that I just kind of hang in there if I'm not having the best day and still try to get the win."
Based on the past few weeks, Williams likes her chances at the Open.
"So there are a lot of things that have to fall in place for me, maybe more than other players," she said. "But I'm up for the challenge."
Her sister struggled to make the switch from Wimbledon's grass, where she won the Olympic singles gold medal as well, to the hard courts.
"I think I'll be OK just getting that match under my belt," Serena Williams said. "I had (42) unforced errors. That's shocking. It's unprofessional. Hopefully I can clean up my act for my next match."
In other matches, third-seeded Samantha Stosur fell behind 4-0 in the third set before rallying for a 6-3, 6-7 (6), 6-4 victory over Spain's Anabel Medina Garrigues, a match that took 2 hours, 37 minutes.
"I thought, 'I can still regroup and close that gap just a little bit,'" Stosur said. "If you can do that, then you never know what can happen. I got on a roll and managed to squeeze it out."
No. 5 Angelique Kerber beat Timea Babos of Hungary 3-6, 6-1, 6-2. Fifteenth-seeded Nadia Petrova retired with dizziness while trailing fellow Russian Ekaterina Makarova 7-6 (8), 3-1.
Tenth-seeded Mardy Fish beat Spain's Feliciano Lopez 6-2, 6-3. No. 11 seed Gilles Simon withdrew before the start of his match against Marcos Baghdatis with a sore shoulder.
Tommy Haas beat David Nalbandian 6-7 (0), 7-6 (4), 6-3 in 3 hours, 22 minutes, equaling the longest non-Olympic match this season on the ATP tour.
AP freelance writer Mark Schmetzer contributed to this report.